Visual function testing is performed to identify and analyze diseases and defects of the cornea, lens, retina, visual neural pathways, and other parts of the eye and vision system. Recently, so-called total immersion, "virtual reality" instruments have been used, for example, to display optical test objects or images to the patient for testing various visual functions of the eye. Generally, such instruments reduce patient fatigue as well as reduce the expense of the instrument. See, for example, U.S. Pat. Nos. 5,550,602 and 5,737,060, which are incorporated herein by reference.
Various types of displays have been used in "virtual reality" instruments, which include the use of large displays, or small, close-proximity displays. Unfortunately, large displays are generally too bulky and/or costly for general use. More recently, however, relatively small, close-proximity displays, such as CRTs or LCDs, have been employed in head-worn units, such as goggles, eyeglasses, and helmets, to display the appropriate visual test objects or stimuli to the patient. In such instruments, suitable optics is housed in the head-worn or head-mounted unit through which the visual test objects are viewed, so as to reduce bulk and/or increase portability.
Unfortunately, some patients have serious hygiene concerns regarding having to share a head-worn or head-mounted instrument, fearing, for example, catching head lice. Others, simply do not like or object to, for vanity reasons, using such visual test instruments, which can disturb their hair.
Accordingly, it is desirable in the art to provide for a multi-functional, close-proximity, total immersion, visual test instrument without the associated problems of the prior art.